This invention relates to phase shifters and more particularly to phase shifters employing a ferrite slab.
As is known in the art, phase shifters have a wide variety of applications in microwave circuits. More specifically, phase shifters have been used in phased array antennas to electronically produce a scanning beam. Of particular interest in these applications is the ferrimagnetic latching phase shifter. It is generally constructed by inserting one or more ferrite toroids in a metal waveguide. Close tolerances must be maintained to avoid the generation of undesirable higher order modes in the minute air gaps between the surfaces of the ferrite and the waveguide. U.S. Pat. Nos. 3,761,845 and 4,001,733 are representative of the schemes developed to avoid this problem. However, they all involve additional manufacturing steps which, in the patents referenced above, require, respectively, wrapping a foil around a composite structure and plating the ferrite assembly.
Another problem of ferrimagnetic phase shifters is that the thermal expansion of the metal waveguide is different from the thermal expansion of the ferrite material. This results in damaging stresses or unwanted movement of the ferrite core within the waveguide in addition to the problems caused by magnetostriction, U.S. Pat. No. 3,849,746 shows a possible mounting method that avoids this problem. However, this also has the disadvantage of requiring additional manufacturing steps.
One solution to this problem, as described in my copending patent application Ser. No. 272,809 filed on June 11, 1983, now U.S. Pat. No. 4,434,409, issued Feb. 28, 1984 includes a dielectric slab disposed adjacent to a ferrite toroid to provide the phase shifter.